1. Technical Field
The present invention relates generally to internal combustion engines and, more particularly to, an automobile engine misfire detection system.
2. Discussion
Misfiring of an automobile engine results in increased emissions into the atmosphere and potential damage of the catalyst. The California Air Resources Board requires that all light duty vehicles be equipped with on-board misfire detectors. Such requirements have spurred much research in misfire detection methods.
A difficulty in the development of an on-board real time misfire detector is the determination of an unified algorithm to detect misfires with high detection accuracy and with no false alarms while maintaining a low implementation cost, under all required engine operating conditions and misfire patterns. These operating conditions include, but are not limited to, different engine speeds, engine loads, road surfaces, gear positions, mechanical dynamics. Furthermore, misfire patterns may be regular, random or special sequences. Because of these challenges, various misfire detection algorithms and methods have been researched and studied in the automotive companies, suppliers, universities and various research institute around the world.
Current methods include those based on such engine characteristics as the engine speed or crankshaft speed. These methods are utilized because of signal availability, overall low implementation cost, and adequate detection performance under most conditions. The typical crankshaft speed based misfire detection methods typically include "frequency" components and engine roughness analysis methods. There are also model based torque and cylinder pressure profile reconstruction methods.